It is known that such turbojets are controlled by a reliable parameter, referred to as a driving parameter, representative of the thrust level of said turbojets and that there are two kinds of driving parameters, one of them being the ratio Engine Pressure Ratio (“EPR”) between the gas pressure at the outlet and at the inlet of the turbojets and the other one being linked to the speed N1 of the fan thereof.
For a determined turbojet, the nature of the driving parameter, that is the ratio EPR or the speed N1, is set by the manufacturer of said turbojet.
It is also known that, preliminarily to the take-off, the turbojets are maintained in an idling speed, with which an idling value of a driving parameter EPR or N1 is associated.
Upon the initiation of the take-off, the pilots of the airplane, thru a voluntary action on the throttle lever, progressively increase the speed of the turbojets, from the idling speed, so as to reach a predefined take-off speed a take-off value of the driving parameter is associated with.
However, it frequently occurs, during the take-off, that the turbojets of an airplane have not all the same current value of the driving parameter at a given moment, although the corresponding throttle levers are in an identical position. Indeed, the acceleration of the fan from the idling speed is likely to vary according to the turbojets of one single airplane, for instance, because:                the mechanical parts of the different turbojets are not lubricated identically;        some turbojets of the airplane have been changed, while the other ones are original ones, so that they do not have all the same wear;        the calibration of the idling speed is not uniform between all the turbojets;        etc.        
This results in an outlet thrust dissymmetry of the turbojets of the airplane able to lead to a side deflection thereof, upon the take-off acceleration, that pilots must imperatively correct. Such a deflection is further even more significant as the speed of the airplane is not very high.
Such direction problems generate, for pilots, an additional workload and an additional vigilance upon a take-off already requiring significant attention.
Moreover, if the correction implemented by pilots is inappropriate or too much delayed, the take-off could be interrupted, thereby disturbing the traffic on the ground.
The aim of the present invention involves overcoming such drawbacks and, more specifically limiting, even removing, the above mentioned direction problems encountered during a take-off.